The field of the invention is electrical switches, and more specifically, electromagnetically operated switches such as relays and line contactors.
Contactors such as that disclosed in U.S. Pat. No. 3,134,869 issued to Leland Lawrence on May 26, 1964, are commonly employed to start and stop electric motors. In such motor starters, the contactor not only opens and closes the main contacts which carry power to the motor, but it also opens and closes auxiliary contacts which connect into control circuits associated with the motor starter. Because such auxiliary contacts do not carry large currents, they are considerably smaller than the main line contacts and are enclosed in cartridges which fasten to the contactor. The auxiliary contacts are coupled to the actuator on the contactor and are spring biased to either a normally opened or normally closed position. The contactor actuator operates the auxiliary contacts when the contactor is energized, and the actuator works against this spring force. The auxiliary contacts thus add additional loading on the electromagnet which operates the actuator.
In addition to the loading which such auxiliary contacts place on the electromagnet, the auxiliary contact cartridges increase the outer dimensions of the contactor. For example, in contactors such as that shown in U.S. Pat. No. 2,919,327 issued on Dec. 29, 1959 to Kuhn et al., the auxiliary contact cartridge extends outward from the contactor increasing its outer dimensions. Because contactors are generally confined in enclosures with other electrical equipment, it is desirable to keep the size of the contactor to a minimum.